Evaporative Concentration Research Articles

Hydrogeochemical Investigations of Groundwater in the Lingbei Area, Leizhou Peninsula

Groundwater is an important source of water supply in the Leizhou Peninsula. In August 2018, five surface water samples, 18 shallow pore water samples, 14 middle-deep pore water samples, and 27 pore fissure water samples were collected in the Lingbei area, the northern part of the Leizhou Peninsula. Major ion concentrations, as well as H, O isotope composition (of δ18O and δ2H) were analyzed. The results show that groundwater pH values, total hardness, concentrations of K+, TDS, Cl-, and SO42- are low, while H2SiO3(aq) and NO3- concentrations are relatively high. For pores and fissures water, hydrochemical types are mainly Mg-Ca-HCO3, Mg-Ca-HCO3-Cl, and Cl- loadings are significantly increased along the flow path. Ca-Cl, Na-Ca-HCO3-Cl, and Na-Ca-Mg-HCO3-Cl types predominate in shallow pore water. For middle-deep pore water, the types are primarily Mg-Ca-HCO3, Na-Ca-Mg-HCO3, K-Na-HCO3-SO4, and concentrations of K+, Na+, Cl-, and SO42- are modestly increased along the flow path. We find that the groundwater is of meteoric origin, groundwater Cl- and Na+ originate from marine atmospheric precipitation, Mg+, Ca2+, and HCO3- are mainly derived from silicate weathering, and NO3- principally arises from chemical fertilizer. Shallow pore water and fissure pore water are affected by evaporation concentration, whereas cation exchange is important for middle-deep pore water. The milligram equivalent ratio of nitrate in groundwater reaches 28.3%. After taking into account the nitrate, 50.85% of the sampling water is NO3 type, and displays a pollution trend. Our results contribute to the sustainable utilization of groundwater in the study area and other similar areas.

Distributed Watershed Hydrological Simulation Method Based on SWAT Model

Liu, D. and Gao, J.N., 2020. Distributed watershed hydrological simulation method based on SWAT model. In: Guido Aldana, P.A. and Kantamaneni, K. (eds.), Advances in Water Resources, Coastal Management, and Marine Science Technology. Journal of Coastal Research, Special Issue No. 104, pp. 738–741. Coconut Creek (Florida), ISSN 0749-0208.Aiming at the problems of large simulation error and long time consumption in traditional distributed hydrological simulation methods, a distributed hydrological simulation method based on SWAT model is proposed in this paper. This paper analyzes the working principle of SWAT model and constructs SWAT model; uses baseline drift method and variable storage coefficient model to extract typical characteristics of groundwater runoff, soil moisture evaporation and water surface concentration of distributed watershed hydrological characteristic data; on this basis, analyzes the spatial distribution characteristics of precipitation, modifies the precipitation coefficient, and through the coefficient of linear regression equation and efficiency coefficient and adjust the root mean square error to realize the distributed hydrological simulation. The experimental results show that the minimum error of the proposed method is about 0.01%, and the maximum simulation time is about 5.8 s.

Quality Assessments of Shallow Groundwaters for Drinking and Irrigation Purposes: Insights from a Case Study (Jinta Basin, Heihe Drainage Area, Northwest China)

This study aimed to determine the hydrochemical characteristics and hydrogeochemical processes of shallow groundwater in the Jinta Basin, northwest China, and to evaluate the suitability of groundwater quality for drinking water and agricultural irrigation. A systematic hydrogeological survey was conducted in the study area from May 2017 to October 2018, during which 123 representative samples of groundwater were selected for analysis of chemical parameters and determination of the water quality index. The results showed that the pH of groundwater in the study area was weakly alkaline and ranged between 7.21–8.93. Dominant cations were Mg2+ and Na+ and the dominant anion was SO42−. Along the groundwater flow from the southwest to northeast, the dominant groundwater chemistry type in the recharge area was Mg-HCO3·SO4. After the transition of the groundwater types in the runoff area to Mg-SO4·HCO3 and Mg·Na-SO4, the groundwater type in the discharge area evolved into Na·Mg-SO4·Cl. The major factors driving the evolution of groundwater chemical types in the Jinta Basin were found to be rock weathering, evaporation and precipitation. The chemical components of groundwater mainly originated from the dissolution of silicate rock and evaporative concentration of salt under water-rock interaction, whereas the dissolution of carbonate had little influence. The quality of drinking water was divided into five groups, and 39.84% of samples fell within the high and good quality groups. The quality of agricultural irrigation water was divided into different grades according to different methods.

Heat-Free Biomimetic Metal Molding on Soft Substrates.

Fabrication of bio-templated metallic structures is limited by differences in properties, processing conditions, packing, and material state(s). Herein, by using undercooled metal particles, differences in modulus and processing temperatures can be overcome. Adoption of autonomous processes such as self-filtration, capillary pressure, and evaporative concentration leads to enhanced packing, stabilization (jamming) and point sintering with phase change to create solid metal replicas of complex bio-based features. Differentiation of subtle differences between cultivars of the rose flower with reproduction over large areas shows that this biomimetic metal patterning (BIOMAP) is a versatile method to replicate biological features either as positive or negative reliefs irrespective of the substrate. Using rose petal patterns, we illustrate the versatility of bio-templated mapping with undercooled metal particles at ambient conditions, and with unprecedented efficiency for metal structures.

Heat‐Free Biomimetic Metal Molding on Soft Substrates

AbstractFabrication of bio‐templated metallic structures is limited by differences in properties, processing conditions, packing, and material state(s). Herein, by using undercooled metal particles, differences in modulus and processing temperatures can be overcome. Adoption of autonomous processes such as self‐filtration, capillary pressure, and evaporative concentration leads to enhanced packing, stabilization (jamming) and point sintering with phase change to create solid metal replicas of complex bio‐based features. Differentiation of subtle differences between cultivars of the rose flower with reproduction over large areas shows that this biomimetic metal patterning (BIOMAP) is a versatile method to replicate biological features either as positive or negative reliefs irrespective of the substrate. Using rose petal patterns, we illustrate the versatility of bio‐templated mapping with undercooled metal particles at ambient conditions, and with unprecedented efficiency for metal structures.

Engineered Celery-Structured Electrospun Fibers Surface and Its Initial Cell Attachment Ability Effect.

The fabrication of various types of scaffolds using electrospinning has been greatly researched for tissue engineering applications in recent times. The rapid initial cell adhesion in electrospun scaffolds helps in the rapid recovery of graft sites. The characteristics of nanofibrous scaffolds can be improved by modifying the topological features and surface of the nanofibers. Previous studies have shown that the scaffold structure is related to a cell attachment ability. In this study, we modified the surface of the fibers to mimic celery structure. It was confirmed that solvent evaporation and polymer concentration influenced the formation of the surface. This structural property can improve the initial adhesion ability of cells. Cellulose acetate solutions were prepared and tested in various concentrations (15 wt%, 20 wt%, and 30 wt%). Scanning electron microscopy (SEM), tensile test and cell experiments were performed to evaluate the physical properties and biocompatibility. The structure of the present nanofiber can be applied as a very effective scaffold and it is expected to have a positive effect in the tissue engineering field.

Experimental study of a novel double-effect evaporation concentration system for high temperature heat pump

In order to solve the problem of energy saving of MVR and energy waste in MEE in the field of low vacuum and low temperature evaporation, a heat pump system and a double effect evaporation concentration system are combined to propose a high temperature heat pump double effect evaporation concentration system. It replaces the high-temperature steam heat source and makes full use of the heat of the last-effect secondary steam, and at the same time realizes the recycling of the intermediate water. In this paper, an industrial experimental platform is designed and built. The experimental results showed: the total evaporation of this system can reach 1985 kg/h, the heat pump COP is 4.92, the unit power consumption evaporation is 11.86 kg/(kW·h). Besides, the thermal characteristics and influencing factors of high-efficiency heat pump double-effect evaporation system are studied, which provides experimental basis and guidance for the practical engineering application, efficient design and optimization of such systems.

Hydrochemical and isotopic characteristics of groundwater in the Jiuquan East Basin, China

To investigate the hydrochemical characteristics and evolution of groundwater in the Jiuquan East Basin, 133 groundwater samples were collected and tested. Statistical analysis, Piper diagram, Gibbs plot, ion ratio and isotope techniques were used to analyse the samples. Our results suggest that both shallow and deep groundwater generally consist of weakly alkaline freshwater, with SO42− and HCO3− as the main anions, and Mg2+ and Na+ as the cations. The shallow groundwater has gradually evolved from the HCO3·SO4–Mg·Ca type in the southern part of the basin (the groundwater recharge runoff area) to the SO4·Cl–Na·Mg type in the northern part of the basin (the groundwater discharge area). Similarly, deep groundwater has progressively evolved from the HCO3·SO4–Mg·Ca type to the SO4·HCO3–Na·Mg type. In the groundwater recharge-runoff area, the chemical components in the shallow and the deep groundwater are mainly originated from the silicate rock weathering, the evaporite rock dissolution and the carbonate weathering. From the groundwater recharge-runoff area to the discharge area, the evaporation concentration, the cation exchange and the adsorption gradually become the main controlling factors of the shallow groundwater hydrochemical composition. The deep groundwater mainly undergoes the leaching, the cation exchange and the adsorption, during the runoff. Furthermore, based on isotope analysis, ice-snow melt water and atmospheric precipitation are identified as the main recharge sources of the shallow and deep groundwater in the area. This paper is great significance for the further protection of water resources and ecological environment, in the area.

Hydrogeological constraints for the genesis of the extreme lithium enrichment in the Salar de Atacama (NE Chile): A thermohaline flow modelling approach

The Salar de Atacama (SdA) is the largest Li reserve globally. The origin of Li, together with the rest of solutes, has been object of debate. Thus, rock weathering at low temperature, hydrothermal leaching or magmatic origin together with subsequent evaporation has been hypothesized. However, the extreme Li enrichment (>4000 mg/L) and the location of the Li-Mg-rich brines around the Salar Fault System (SFS) that crosses the nucleus of the SdA in half remain unexplained. The objective of this work is to define the thermohaline groundwater flow in the SdA basin to account for the genesis of its extreme Li enrichment.Thermohaline flow modelling has demonstrated the critical effect of the minimum hydraulic head (MHH) of the regional water table on the groundwater flow of salt flats. The MHH divides the basin into two isolated hydrodynamic systems and constitutes the endpoint towards which the most evaporated brines converge. The spatial mismatch between the locations of the Li-Mg-rich brines in the central-western zone of the nucleus (in the SFS) and the MHH in the easternmost zone of the nucleus discards recent evaporative concentration of the recharge water as the main mechanism of Li enrichment. Moreover, the persistence of a saline interface surrounding the nucleus at depth, regardless of the temperature gradient, also precludes lateral recharge (predominantly from the east) to ascend along the SFS.On the other hand, the computed thermohaline flow is compatible with the remobilization of buried layers of Li-Mg-enriched salts and/or clays by dilute recharge waters coming from the west or southwest of the basin. Here, the role of faults and density-driven flow is key to allow efficient downward and upward flow rates that favour the remobilization of Li and Mg.

Fluoride occurrence in United States groundwater

Data from 38,105 wells were used to characterize fluoride (F) occurrence in untreated United States (U.S.) groundwater. For domestic wells (n = 11,032), water from which is generally not purposely fluoridated or monitored for quality, 10.9% of the samples have F concentrations >0.7 mg/L (U.S. Public Health Service recommended optimal F concentration in drinking water for preventing tooth decay) (87% are <0.7 mg/L); 2.6% have F > 2 mg/L (EPA Secondary Maximum Contaminant Level, SMCL); and 0.6% have F > 4 mg/L (EPA MCL). The data indicate the biggest concern with F in domestic wells at the national scale could be one of under consumption of F with respect to the oral-health benchmark (0.7 mg/L). Elevated F concentrations relative to the SMCL and MCL are regionally important, particularly in the western U.S. Statistical comparisons of potentially important controlling factors in four F-concentration categories (<0.1–0.7 mg/L; >0.7–2 mg/L; >2–4 mg/L; >4 mg/L) at the national scale indicate the highest F-concentration category is associated with groundwater that has significantly greater pH values, TDS and alkalinity concentrations, and well depths, and lower Ca/Na ratios and mean annual precipitation, than the lowest F-concentration category. The relative importance of the controlling factors appears to be regionally variable. Three case studies illustrate the spatial variability in controlling factors using groundwater-age (groundwater residence time), water-isotope (evaporative concentration), and water-temperature (geothermal processes) data. Populations potentially served by domestic wells with F concentrations <0.7, >0.7, >2, and >4 mg/L are estimated to be ~28,200,000, ~3,110,000; ~522,000; and ~172,000 people, respectively, in 40 principal aquifers with at least 25 F analyses per aquifer.

Separation and recovery of arsenic and alkali products during the treatment of antimony smelting residues

For the comprehensive utilization of antimony smelting arsenic-alkali residue, there are some problems such as the incomplete separation and low recoveries of arsenic and alkali, and the formation of arsenic-alkali mixed salts with secondary pollution. In order to solve these problems, the leaching solution of arsenic-alkali residue (arsenic-alkali solution) was used as a raw material in this study, and a novel process of twice alkali recovery with CO2, deep alkali removal with H2SO4, As(V) reduction with SO2 and evaporation concentration to recover arsenic was proposed to dispose of the arsenic-alkali solution. The total recovery of alkali was 87.8% by twice alkali recovery from the arsenic-alkali solution. After washing and thermal decomposition of crude NaHCO3, the obtained Na2CO3 product can be used as the reagent of arsenic removal in the refining process of crude antimony. In the process of deep alkali removal, compared with the direct treatment, the consumption of H2SO4 after twice alkali recovery was markedly reduced from the arsenic-alkali solution, and also no mirabilite was precipitated. The total recovery of arsenic was 80.6% in the process of arsenic recovery, and the purity of As2O3 in arsenic trioxide product reached 95.2% after washing, which meets the third grade standard of arsenic trioxide (GB 26721–2011). This process realizes the efficient separation and recovery of arsenic and alkali from the arsenic-alkali solution, and also no arsenic-alkali mixed salts are produced.

The Formation of Clay Minerals in the Mudflats of Bolivian Salars

AbstractUnderstanding clay-mineral assemblages forming in saline lakes aids in reconstructing paleoenvironments on Earth and other terrestrial planets; this is because authigenic phyllosilicates are sensitive to the prevailing geochemical conditions present during formation. In most geochemical models, evaporative concentration favors sepiolite with increasing silica and Mg2+ concentrations without considering the role of the biogenic removal of silica from solution by diatoms. In the present study, phyllosilicates occurring in the mudflats of Bolivian salars were investigated to aid in understanding the geochemical factors that control mineral assemblages forming in (SO42–)- and (Cl–)-rich environments in relation to dissolved silica. From transects across the mudflats, the physical, chemical, and mineralogical characteristics of the bulk sediment and the &lt;2 μm fraction of each sedimentary layer were analyzed. From these analyses, three types of sediments were identified: (1) regolith sediments dominated by Al-dioctahedral smectite, illite, and chlorite; (2) detritus-rich mudflat sediments with Mg-trioctahedral smectite and Al-dioctahedral smectite along with illite and chlorite; and (3) authigenic mudflat sediments dominated by poorly formed Mg-trioctahedral smectite, kerolite, and biogenic silica. The absence of sepiolite-palygorskite in the salars is the result of excessively high Mg:Si ratios within the waters. In the surface water Mg becomes enriched relative to Si as diatoms remove dissolved Si from solution through biologically mediated uptake. The geochemical conditions present within the salars that act to preserve the diatom frustules and prevent their dissolution include: neutral–slightly alkaline pH solutions, cold temperatures, shallow water, and high salinity. Under these conditions the formation of sepiolite is restricted by the small amount of dissolved silica, despite the silica-rich environment. The formation of Mg-smectite and kerolite is favored under these conditions.

Origin and signs of disturbance of hyperarid climate wetland ecosystem: case of Chott Ain Beida, Algerian Sahara

Chott Ain Beida is an inland sabkha located in southern Algeria. Close to Ouargla city, it is surrounded by an exploited palm groove. In this study, modern climate of Ouargla region updated, surficial geology determined and geochemistry of its brines studied relative to geogenic factors and anthropogenic stress. Mean temperature increased by 2 °C, and thermal amplitude by 1.5 °C. The surficial lithology consists of eolian sand, evaporites and rich-organic matter clay. It is characterized by a rapid vertical and lateral changes which make some areas isolated and others communicating to drainage network and shallow/deep-water springs. This induced the heterogeneity of brines over the chott. The insulate areas show high total dissolved solids (> 230 g/L), high concentration factor (4 ÷ 8), high ionic strength (> 3), high Cl−/SO42 ratio (> 2.3) and high Mg2+/Ca2+ ratio (> 3), while the communicating areas present lower values of the same parameters. The diluted brines are Na+ + Mg2+_sulfate and have undergone an evaporative concentration geochemical process while the concentrated others are Na+ + Mg2+_chloride and show the cessation of evaporation process. The positive saturation indices reveled the occurrence of vaterite which is confirmed by the results of X-ray powder diffraction and energy-dispersive X-ray spectroscopy. Vaterite formation was possible after the combination of all the necessary reagents, namely presence of calcium, bicarbonate, phosphate, ammonium and carbone dioxide gas. These chemical reagents are provided by organic and mineral pollution. Vaterite formation begins with the presence of ammonium and remains more than 250 h before its transformation to calcite. Its formation sequestered important quantities of carbon dioxide.

Li and Ca Enrichment in the Bristol Dry Lake Brine Compared to Brines from Cadiz and Danby Dry Lakes, Barstow-Bristol Trough, California, USA

Relatively few discharging playas in western United States extensional basins have high concentrations of lithium (Li) and calcium (Ca) in the basin-center brines. However, the source of both these ions is not well understood, and it is not clear why basins in close proximity within the same extensional trough have notably different concentrations of Li and Ca. In the Barstow-Bristol Trough, California, USA, three playas in separate topographically closed basins vary in Li and Ca concentrations from northwest to southeast: 71–110 mg/L Li and 17–65 g/L Ca at Bristol Dry Lake, 20–80 mg/L Li and 7.5–40 g/L Ca at Cadiz Dry Lake, and &lt;5 mg/L Li and &lt;0.5 g/L Ca at Danby Dry Lake. Using new and historic data from recently drilled wells (2017–2018), it has been determined that there is minimal variation of temperature, Li, and major ion concentrations with depth (down to 500 m), suggesting that the brines are well mixed and likely to circulate slowly due to density driven flow. Although it has been postulated that geothermal fluids supply the Li and Ca to Bristol and Cadiz closed basins, there is little to no surface evidence for geothermal fluids, except for a young (80,000-year-old) volcanic crater in Bristol Dry Lake. However, major-ion chemistry of fluid inclusions in bedded halite deposits show no change in brine chemistry over the last 3 million years in Bristol Dry Lake indicating that the source of lithium is not related to these recent basaltic eruptions. Mg–Li geothermometry of basin-center brines indicates that Bristol and Cadiz brines have possibly been heated to near 160 °C at some time and Danby brine water has been heated to less than 100 °C, although Cadiz and Danby lakes have no known surface geothermal features. The difference in Li concentrations between the different basins is likely caused by variable sources of both ions and the hydrology of the playas, including differences in how open or closed the basins are, recharge rates, evaporative concentration, permeability of basin-center sediments, and the possible amount of geothermal heating. The differences in Ca concentrations are more difficult to determine. However, historic groundwater data in the basins indicate that less saline groundwater on the north side of the basins has molar Ca:HCO3 and Ca:SO4 ratios greater than one, which indicates a non-saline groundwater source for at least some of the Ca. The similar Li and Ca concentrations in Bristol and Cadiz lakes may be because they are separated only by a low topographic divide and may have been connected at times in the past three million years. All three basins are at least Miocene in age, as all three basins have been interpreted to contain Bouse Formation sediments at various depths or in outcrop. The age of the basins indicates that there is ample time for concentration of Li and Ca in the basins even at low evaporation rates or low geothermal inputs. The source of Li for brines in Bristol and Cadiz basins is postulated to be from ancient geothermal fluids that no longer exist in the basin. The source of Li to the sediment may be either geothermal fluids or dissolution and concentration of Li from tephra layers and detrital micas or clays that are present in the sediments, or a combination of both. The source of Ca must at least partially come from groundwater in the alluvial fans, as some wells have Ca:HCO3 ratios that are greater than one. The source of Ca could be from the dissolution of Ca-bearing igneous rocks in the surrounding catchments with limited HCO3 contribution, or dilute geothermal water migrating up through faults in the basin margin. The relatively low concentration of Li and Ca in Danby playa is likely caused by a lack of sources in the basin and because the basin was (or is) partially hydrologically open to the south, reducing the effectiveness of evaporative concentration of solutes. Bristol Dry Lake is likely the only hydrologically closed basin of the three because although Cadiz has a similar brine chemistry and salinity, there is almost no halite deposition in the basin. It is only Bristol Dry Lake that contains 40% halite in its basin center.

Hydrogeochemical Characteristics and Health Effects of Iodine in Groundwater in Wei River Basin

Existing studies show that drinking high-iodine or low-iodine groundwater on a long-term basis may cause goiter and other health problems. However, currently there is a lack of systematic research on the distribution, formation and health effects of iodine in groundwater at the basin scale. Taking the Wei River Basin in the Loess Plateau as a typical study area, this paper used hydrogeological surveys, sample collection, multivariate statistical analysis, health effect evaluations, and other methods, and found that iodine content in groundwater in 60.3% of the region poses potential risks to human health. Groundwater recharge areas were iodine-deficient, mainly located on the upstream Loess Plateau of the Wei River Basin in the vicinity of the Liupan Mountain watershed, and at the piedmont of the Qinling Mountains. Groundwater was low mineralization, neutral, and low-F bicarbonate, and was controlled by the weathering and dissolution of silicate minerals and evaporites, the dissolution and precipitation of carbonates, and active water circulation conditions. Iodine-deficient endemic goiter had a potential incidence of 5–38% in these areas. Groundwater runoff areas had suitable groundwater iodine content, and the groundwater hydrochemical type was dominated by HCO3–Ca, HCO3–Na, and HCO3·SO4–Na type water. The mineralization degree was modest and the I− content distribution of suitable iodine content areas was controlled by relatively active water circulation conditions. Groundwater discharge areas were high-iodine groundwater areas, where the groundwater hydrochemical type was dominated by meta-alkaline and alkaline HCO3·SO4, SO4·Cl, and Cl·SO4 type water, and controlled by the evaporation–concentration of shallow groundwater, the biodegradation of enriched organic matter, and the competitive adsorption of HCO3− and I−. Here iodine-excess endemic goiter had a potential incidence of 5–100%. Considering the results from the study area, this paper recommends that the groundwater iodine safety range for endemic goiter be set to 10.0–300.0 μg/L.

Ultrafast laser micro-nano structured superhydrophobic teflon surfaces for enhanced SERS detection via evaporation concentration

Abstract Evaporation concentration of target analytes dissolved in a water droplet based on superhydrophobic surfaces could be able to break the limits for sensitive trace substance detection techniques (e.g. SERS) and it is promising in the fields such as food safety, eco-pollution, and bioscience. In the present study, polytetrafluoroethylene (PTFE) surfaces were processed by femtosecond laser and the corresponding processing parameter combinations were optimised to obtain surfaces with excellent superhydrophobicity. The optimal parameter combination is: laser power: 6.4 W; scanning spacing: 40 μm; scanning number: 1; and scanning path: 90 degree. For trapping and localising droplets, a tiny square area in the middle of the surface remained unprocessed for each sample. The evaporation and concentration processes of droplets on the optimised surfaces were performed and analyzed, respectively. It is shown that the droplets with targeted solute can successfully collect all solute into the designed trapping areas during evaporation process on our laser fabricated superhydrophobic surface, resulting in detection domains with high solute concentration for SERS characterisation. It is shown that the detected peak intensity of rhodamine 6G with a concentration of 10−6 m in SERS characterisation can be obviously enhanced by one or two orders of magnitude on the laser fabricated surfaces compared with that of the unprocessed blank samples.

Water quality and health risk assessment of shallow groundwater in the southern margin of the Tarim Basin in Xinjiang, P. R. China

In this study, 266 shallow groundwater samples were collected, and pH, TH, TDS, concentrations of main cations (K+, Na+, Ca2+ and Mg2+), main anions (Cl−, SO4 2− and HCO3 −), NO2-N, NO3-N, NH4-N, F−, As, Fe, Cu, Mn, Zn, Hg, Cr6+, Pb and Cd were analyzed to assess the quality and health risk of shallow groundwater in the southern margin of the Tarim Basin. Results showed that groundwater in the study area was weak alkaline with hydrochemistry type by SO4•Cl-Ca•Mg and SO4•Cl-Na primarily. Groundwater chemical characteristics were mainly affected by rock weathering and evaporation concentration. Groundwater in this area is unsafe for drinking due to poor water quality, which mainly affected by natural environment as well as industrial and agricultural activities. Total carcinogenic risk and total non-carcinogenic risk of shallow groundwater in the study area were high, which exceed acceptable health risk level. The order of non-carcinogenic health risks from high to low were Cr6+, Cd, F−, As, Cu, Fe, Pb, Hg, NO3-N, Mn, NO2-N, NH4-N, and Zn, and the order of carcinogenic health risks were Cr6+, Cd and As, among which Cr6+, Cd, F− and As were the main indicators of healthy risk management controls.

A critical analysis of electrospray techniques for the determination of accelerated rates and mechanisms of chemical reactions in droplets.

Electrospray and Electrosonic Spray Ionization Mass Spectrometry (ESI-MS and ESSI-MS) have been widely used to report evidence that many chemical reactions in micro- and nano-droplets are dramatically accelerated by factors of ∼102 to 106 relative to macroscale bulk solutions. Despite electrospray's relative simplicity to both generate and detect reaction products in charged droplets using mass spectrometry, substantial complexity exists in how the electrospray process itself impacts the interpretation of the mechanism of these observed accelerated rates. ESI and ESSI are both coupled multi-phase processes, in which analytes in small charged droplets are transferred and detected as gas-phase ions with a mass spectrometer. As such, quantitative examination is needed to evaluate the impact of multiple experimental factors on the magnitude and mechanisms of reaction acceleration. These include: (1) evaporative concentration of reactants as a function of droplet size and initial concentration, (2) competition from gas-phase chemistry and reactions on experimental surfaces, (3) differences in ionization efficiency and ion transmission and (4) droplet charge. We examine (1–4) using numerical models, new ESI/ESSI-MS experimental data, and prior literature to assess the limitations of these approaches and the experimental best practices required to robustly interpret acceleration factors in micro- and nano-droplets produced by ESI and ESSI.

Arsenic in water, sediment, and fish of lakes from the Central Tibetan Plateau

As a potential source of arsenic (As) for the downstream region of the South and East Asia, the As contamination in the Qinghai-Tibet Plateau (QTP) still needs more investigation. In this study, As concentrations in the surface water, lake sediments, and fish of lakes and endorheic rivers in the central Tibet Plateau (CTP) were investigated for the better understanding of As fate in the CTP. Extremely high levels of As in saline lakes water were found with concentrations up to 10,775.40 μg/L, while the lowest level of As was found in freshwater lakes with a concentration of only 1.80 μg/L. Natural loading and evaporation concentration were the main reasons for As accumulation in saline lakes in the CTP. Rock weathering and terrestrial ecosystem could affect the As level in the lake. As contents in lake sediments significantly positive related to the As/EC ratios but showed no correlation with As concentrations in the water. Although As levels in the fish were higher in lakes with higher As concentrations, they were still lower than those of the fish from As-contaminated lakes in other studies. Results of this study indicate that hot spots of As in the CTP require more in-depth attention and studies in the future to better understand their influence on the fragile CTP aquatic ecosystem.

A coupling technology of capacitive deionization and MoS2/nitrogen-doped carbon spheres with abundant active sites for efficiently and selectively adsorbing low-concentration copper ions

Conventional techniques like electrodialysis, evaporation concentration cannot efficiently and selectively separate valuable heavy metals ions (VHMI) from electroplating rinse wastewater due to VHMI’s low concentration and other ions’ competitive adsorption. To realize the separation, a coupling technology was proposed which combines capacitive deionization (CDI) technique suitable for separating low-concentration ions and the few-layer molybdenum disulfide/N-doped carbon spheres (FL-MoS2/NCS) composite capable of selectively adsorbing copper ions (Cu2+), a representative VHMI. The FL-MoS2/NCS composite was successfully prepared by one-pot method and used as the cathode and anode in a CDI cell. Electrosorption experiments in the CDI cell showed that the FL-MoS2/NCS electrode (cathode) can efficiently adsorb low-concentration Cu2+ (23.63 mg/L) with a saturated adsorption capacity of 1199.63 mg/g at 0.8 V. In the competitive environment (Cu2+/Na+/Fe3+), the FL-MoS2/NCS electrode can selectively adsorb Cu2+ still with a high adsorption capacity of 1071.6 mg/g greatly outnumbering that of Na+ (199.2 mg/g) and Fe3+ (262.8 mg/g), despite the high concentrations of both NaCl (500 mg/L) and FeCl3 (80 mg/L). Furthermore, the XPS test and competitive adsorption results proved that the efficient and selective adsorption of the FL-MoS2/NCS electrode for Cu2+ was synergistically promoted by electrical double layer (EDL) and complexation of Cu2+ with FL-MoS2/NCS.